Method of obtaining electrical insulation and the product



Rv E. BISHOP METHOD OF OBTAINING ELECTRICAL INSULATION AND THE PRODUCTJune 6, 1939.

Filed Dec. 11, 1937 Patented June 6, 1939 UNITED STATES PATENT OFFICEMETHOD OF OBTAINING ELECTRICAL IN- SULATION AND THE PRODUCT ApplicationDecember 11, 1937, Serial No. 179,376

4Claiml.

This invention is concerned with improved methods and products foreffecting the insulation of electrical connections, apparatus and thelike, and the product.

The general object of the invention is to provide a new method andproduct and concerned with the insulation of electrical connections andapparatus of all kinds, and particularly with methods of electricallyinsulating circuit joints and connections while energized.

The many detailed objects of this invention will be apparent from thefollowing disclosure, particularly when taken in connection with theattached drawing which is presented in an illustrative sense.

This invention resides substantially in the combination, construction,arrangement, relative location of parts, steps and series of steps, allas will be fully described in this specification.

In the accompanying drawing,

Figure 1 is a longitudinal, central, cross-sectional view through acable joint insulated in accordance with the method of this invention;

Figure 2 is a similar view of a further modification; and I Figure 3 isan outside elevational view of the joint of Figure 2.

At the present time the most common method of insulating freshly madejoints in wires and cables, and of the exposed parts of electricalapparatus consists in wrapping the exposed metal parts with many layersof insulating tape which is employed in several well known forms.Frequently there is interposed between the adjacent layers of tapeinsulating, and/or adhesive varnishes, strips of insulating fabric suchas varnished cambric, oiled silk, and the like. The building up of asatisfactory insulation of this type which is very commonly done in thefield, involves a considerable amount of time and skilled operators whoare highly paid. The result is that joints insulated in this manner areexpensive.

Since this work must frequently be carried on while the metal parts orcircuits are energized,

no more satisfactory method than this has heretofore been devised. Thereare of course known and used types of premolded or cast insulatingfittings or castings which have been used, but

since they are often of necessity formed of two mating parts they arenot sufficiently watertight, especially when used in the fleld such'asin manholes in the street, to permit of very extensive use thereof. Inaddition, although they save 66 time in installation they are ofnecessity'rather expensive. The result is, because of their cost andineffectiveness in many places they are not very extensively used.

The invention herein disclosed involves the use of materials novel forthis purpose, and methods of employing them which make their use for thefirst time possible and practical. As noted above, the insulation ofexposed metal parts in electrical circuits, and particularly wire andcable joints, must often be applied while the metal parts are energized,with the result that heretofore fluid containing insulating materials,and particularly those containing water or moisture have not beenavailable for use because of the almost certain injury which would occurto the operator in applying them to the energized parts. However, bymeans of this invention this may now be accomplished in a number ofdifferent ways, employing highly insulating materials particularlydesirable for the purpose, in a manner so as to form a continuoushomogeneous body of insulation surrounding the metal parts, and in thecase of cables bonded to portions thereof to form a thoroughlywatertight seal of high protective characteristics.

In accordance with this invention latices of various forms andparticularly latex in combination with various ingredients in mixturetherewith are employed. Admixed to latex for example is a suitablenon-conducting, moisture-absorbing ingredient, preferably in powderform, such as aluminous cement or its equivalent. In addition whendesired moisture-absorbing fibrous materials such as jute, hemp,asbestos, and the like may be incorporated into the mass which inaddition impart some additional strength thereto. Furthermore, whendesired there may be added to the mixture various materials commonlyemployed with rubber latices to act as hardening, setting andvulcanizing agents, and when iurther desired, agents which acceleratethese actions. Such materials are well known in the arts in many forms.Instead of latex, rubber dissolved in various volatile solvents knownfor the purpose, or prevulcanized rubber may be employed in combinationwith the ingredients mentioned above in connection with the use oflatex, as well as with various volatile solvents.

Fluid plastic masses of latices of the above described forms areconducting, with the result that they have not heretofore found use forthe purpose of insulating exposed metal parts in electrical circuits. 0nthe other hand, they have many desirable characteristics for the purposebut heretofore no method has been available for using them.

There are disclosed in the attached drawing methods which now make themavailable for these purposes. By way of illustrating the princasing 2,both of which of course have been removed to expose the ends 3 and 3 ofthe cable, wire, or conductor to be united. In the drawing these endshave been shown as united, and it is immaterial to this disclosure as tothe manner in which this has been done. Surrounding the exposed metal ofthe conductor is a thin layer 6 of a rapidly drying and/ornon-conducting material such as a bituminous base insulating compound ofwhich many forms are known, an insulating varnish such as for exampleone having a gum base, a wax compound, rubber in tape or sheet form,varnished cambric, oiled silk, or any other electrical insulatingmaterial which is in itself non-conducting at the time of application orvery quickly thereafter becomes non-conducting. It is preferable thatthis layer 6 extend beyond and overlap a short distance the ends of theinsulation 2 as shown at 6. As is clear from Figure 1, the layer 6completely encloses the exposedmetal portion of the cable, and in thecase where the operator is working on live circuits, this layer affordsadequate protection to him for the following operation. I

'Encasing the portions 2 and 6 and partly overlapping the ends of theportions I is a covering or housing which is composed for example, as

explained above, of latex in admixture with a moisture-absorbing agentsuch as aluminous ce-- ment in powder form, and if desired fibrousmaterials such as hemp, jute, asbestos and the like,

with or without the addition of a suitable hardening, setting orvulcanizing agent. A mixture of these ingredients of suitableconsistency is made up and the operator then molds a mass of it aroundthe joint, as is clearly shown in Figure 1, to form a continuoushomogeneous casing I for the joint which he may work with his handswithout danger of injury even on live circuits because of the protectionofiered by the layer 6. Plastic materials of this nature may be. made upin consistencies which make it possible to mold the material in thismanner and have it hold its shape during the period while it is setting,hardening or vulcanizing. The molded mass becomes bonded or welded tothe exposed rubber casings 2, which action may be accelerated by firstpainting them, if desired, with a suitable bonding agent having a rubberbase such as forexample rubber cut in a volatile solvent. Thus, althoughthe mass is a continuous homogeneous body which as soon as it sets willnot break loose from the joint, its attachment thereto is furtherinsured by its bond to the portions 2 of the cable.

At this point it may be well to emphasize that the invention hereindisclosed is shown as applied to exposed conductors in a circuit, butmay of course be employed to insulate any exposed metal parts ofelectrical apparatus, and indeed any other apparatus not only toinsulate it, but

In Figure 1 it will be seen that the outer' to protect it againstinjury, corrosion and the like.

Figures 2 and 3 show a further method of accomplishing the objects ofthis invention. In Figure 2 the insulating layer or film 6 has beenused, but it is pointed out that it may in the proper cases beeliminated. In addition the film 6 in this arrangement may be eliminatedeven in the case of live circuitsbecause the plastic composition 1,prepared as explained above in connection with Figure 1, is placed insuitable quantity in a preformed thin insulating shell comprising themating parts 8 and 9. This shell may be made of any suitable materialeither moisture absorbent or resistant. It may, for example, be made ofpressed wood pulp, or any .one' of the synthetic plastic materials suchas Bakelite. The two halves containing the rubber mass are clampedaround the joint so that the mating shell portions are aligned. It maythen be held in place by wrapping a suitable binder around it until therubber has set, and if desired to more certainly insure a watertightjoint, the line of union between the shell parts may have appliedthereover an insulating film as indicated at III. This film can be anyof the materials referred to as comprising the film 6 of Figure 1, whichin the case of volatile solvents will quickly dry, or in the case ofmelted asphalt compounds will quickly cool and set to seal the joint.

When desired, as noted above, the arrangements of Figures 2 and 3 mayinclude the film 6. For further emphasis this film in all forms of theinvention either consists of asphalt and/or pitches having a low meltingpoint, which may be easily melted, applied hot, and which quickly cooland solidify. It may be of waxfin paste form, or a petroleum productsuch as petrolatum, or jellies or oils having high insulating qualities.It may be formed of sheets of rubberized or treated' fabric such asoiled silk or varnished cambric. It may be built up of a layer offriction or rubber tape which may be used in a much lesser quantity andbuilt more quickly than in the case where the entire insulation is madeup therefrom. It is believed that on the basis of the above thoseskilled in the art will readily appreciate the equivalency for thepurpose of other known materials.

It is of course to be appreciated that the form of joint illustrated inthe drawing is exceedingly simple, whereas in actual practice thesejoints are often quite complicated, as in the case where more than twowires come together and often at dlflicult angles. The advantage of thisinvention becomes even more readily apparent when considered inconnection with complicated and intricate joints where-the most skilland longest time is required to adequately tape and protect them by theolder methods, The insulating composition herein disclosed can be easilymolded around the joint and the part even in cases where it is an undulycomplicated one.

From the above description it will be apparent to those skilled in theart that the methods of this invention and the details of the productsthereof may be widely varied without departure from the novel subjectmatter herein disclosed.

I do not, therefore, desire to be strictly limited to the disclosure asgiven for purposes of illustration, but rather to the scope of theappended claims.

What I seek to secure by United States Letters Patent is:

1. A method oi insulating .a live electrical conductor which comprisesencasing the conductor within a thin insulating layer and molding aplastic rubber mass therearound capable of setting, which is conductivewhile plastic and insulating when set to form an insulating protectiontherefor.

,2. A method oi insulating an exposed joint between a pair oi rubberinsulated cables in a live electric circuit'which comprises applying aninsulating film to the exposed Joint and molding therearound aplasticrubber mass capable of setting which is conductive while plastic andinsulating when set and bonded to the rubber insu- 1. luation of saidcables.

3. A method of insulating and waterproofing an exposed portion of anelectric cable vhile in circuit including the steps of applying a liquidinsulating coating to the exposed portion thereof and molding thereovera plastic rubber base mass capable of setting which is conductive whileplastic and insulating when set to form an insulating and waterproofprotection therefor.

4. A method of insulating and waterproofing a joint between a pair ofrubber insulated cables comprising the step of encasing the exposedmetal joint within an insulating. casing and molding a plastic rubberbase mass therearound capable oi setting which is conductive 'whileplastic and insulating and waterproofing when set.

RICHARD E. BISHOP.

